Method for forming barrier layer and method for manufacturing semiconductor device

ABSTRACT

In a method for forming a barrier layer, the barrier layer is formed on a base layer having a three-dimensional structure before a dopant-containing layer is formed on the base layer. At this time, at least one of a film thickness, a film quality, and a film type of the barrier layer is controlled in a height direction of the three-dimensional structure by using an atomic layer deposition (ALD) process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. Provisional Application No. 63/005,156, filed on Apr. 3, 2020 in the United States Patent and Trademark Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to a method for forming a barrier layer and a method for manufacturing a semiconductor device, and more particularly, to a method for forming a barrier layer which is used for doping a base layer in a manufacturing process of a semiconductor device such as a FinFET.

Description of Related Art

Conventionally, with high integration of a semiconductor chip, miniaturization, a high-speed operation, and low power consumption of a planar transistor such as a MOSFET have been progressed. However, in a conventional planar transistor, a so-called short channel effect, which cannot control an operation by a gate voltage when a channel length is miniaturized, cannot be suppressed, and thus there is a limitation to minimize the planar transistor. Therefore, research and development of a three-dimensional transistor including a fin field effect transistor (hereinafter, also referred to as FinFET) have been widely made.

Since the three-dimensional transistor has a three-dimensional structure in which a gate electrode surrounds a channel portion, the three-dimensional transistor has more excellent controllability to a channel region of the gate electrode than that of the conventional planar transistor, and is more suitable for miniaturization than the planar transistor. Further, due to the excellent controllability, the three-dimensional transistor can realize a high-speed operation and low power consumption characteristics beyond the planar transistor, and further contributes to a reduction in a pattern area.

On the other hand, the three-dimensional transistor has a more complicated structure than the planar transistor, resulting in development and complication of manufacturing technology, and an increase in manufacturing costs. However, due to a recent advance in microfabrication technology, it is possible to manufacture a three-dimensional transistor while minimizing the increase in manufacturing costs, and accordingly, it is expected that the three-dimensional transistor is used for various system large scale integrations (LSIs) in various industrial fields.

A FinFET, which is an example of a three-dimensional transistor, has one or more fins formed in a channel region between source-drain electrodes and provided on a silicon substrate. The gate electrode is formed to straddle one or more fins and has a so-called double gate structure. Due to this double gate structure, the FinFET has more excellent controllability as described above compared to the MOSFET having a single gate structure.

A method for forming a dopant-containing layer for doping top and side surfaces of one or more fins by using atomic layer deposition (ALD) is proposed for the purpose of forming an extension electrode of a FinFET or the like (see United States Patent Application Publication No. 2015/0249013). The ALD is a film forming method of forming an atomic layer on a substrate surface in one atomic unit by self-control, and it is possible to form an ultrathin film. Therefore, when a groove having a high aspect ratio (depth dimension/width dimension) is formed in the channel region due to the complication of a fin structure, the ALD is effective to form the dopant-containing layer uniformly on the top and side surfaces of the fin as compared to another method such as CVD or PVD.

In recent years, it is required to form a three-dimensional structure having a higher aspect ratio in the channel region in order to meet a demand for higher performance and densification of a device. However, when the aspect ratio is high, a film thickness of a dopant-containing layer 120A formed in an upper region 100 a of a base layer 100 having a three-dimensional structure is likely to be large, and a film thickness of the dopant-containing layer 120A formed in a lower region 100 b is likely to be small, as illustrated in FIG. 10 . Alternatively, a concentration of a dopant in a dopant-containing layer 120B formed in the upper region 100 a having a top surface of the base layer 100 is likely to be high, and a concentration of a dopant in the dopant-containing layer 120B formed in the lower region 100 b is likely to be low. As a result, there is a problem that the dopant in the base layer 100 after drive-in is distributed non-uniformly in a height direction of the base layer. That is, it is considered that such non-uniformity is caused by non-uniformity of the coating of the dopant-containing layer itself or non-uniformity of the concentration of the dopant in the dopant-containing layer.

SUMMARY OF THE INVENTION

[1] A first aspect of the present disclosure provides a method for forming a barrier layer on a base layer having a three-dimensional structure before a dopant-containing layer is formed on the base layer, the method including: controlling at least one of a film thickness, a film quality, and a film type of the barrier layer in a height direction of the three-dimensional structure by using an atomic layer deposition (ALD) process.

[2] The method for forming a barrier layer according to the above-described [1], in which the atomic layer deposition process is a plasma enhanced atomic layer deposition (PEALD) process.

[3] The method for forming a barrier layer according to the above-described [2], in which the film thickness of the barrier layer formed on side surfaces of the three-dimensional structure is controlled by adjusting an application time of RF power.

[4] The method for forming a barrier layer according to the above-described [2], in which the film thickness of the barrier layer formed on a top surface of the three-dimensional structure is controlled by adjusting RF power and an application time of the RF power.

[5] The method for forming a barrier layer according to the above-described [2], in which the film quality of the barrier layer is controlled by adjusting RF power and an application time of the RF power.

[6] The method for forming a barrier layer according to the above-described [2], in which the film type of the barrier layer is controlled by forming the barrier layer with SiN having area selectivity or forming the barrier layer with SiON and adjusting a concentration of element N.

[7] The method for forming a barrier layer according to the above-described [1], in which the three-dimensional structure includes a trench, and an aspect ratio (height dimension/width dimension) of the trench is 10 to 100.

[8] A second aspect of the present disclosure provides A method for manufacturing a semiconductor device, including: a step (A) of forming a base layer having a three-dimensional structure; a step (B) of forming a barrier layer on the base layer; a step (C) of forming a dopant-containing layer on the barrier layer by using an atomic layer deposition (ALD) process; and a step (D) of performing a heat treatment, in which in the step (B), at least one of a film thickness, a film quality, and a film type of the barrier layer is controlled in a height direction of the three-dimensional structure by using the atomic layer deposition process, and in the step (D), a dopant contained in the dopant-containing layer is diffused into the base layer through the barrier layer.

[9] The method for manufacturing a semiconductor device according to [8], in which in the step (B), the atomic layer deposition process is a plasma enhanced atomic layer deposition (PEALD) process.

[10] The method for manufacturing a semiconductor device according to [8], in which in the step (B), the film thickness of the barrier layer formed on side surfaces of the three-dimensional structure is controlled by adjusting an application time of RF power.

[11] The method for manufacturing a semiconductor device according to [8], in which in the step (B), the film thickness of the barrier layer formed on a top surface of the three-dimensional structure is controlled by adjusting RF power and an application time of the RF power.

[12] The method for manufacturing a semiconductor device according to [8], in which in the step (B), the film quality of the barrier layer is controlled by adjusting RF power and an application time of the RF power.

[13] The method for manufacturing a semiconductor device according to [8], in which in the step (B), the film type of the barrier layer is controlled by forming the barrier layer with SiN having area selectivity or forming the barrier layer with SiON and adjusting a concentration of element N.

[14] The method for manufacturing a semiconductor device according to [8], in which in the step (C), the atomic layer deposition process is a plasma enhanced atomic layer deposition (PEALD) process.

[15] The method for manufacturing a semiconductor device according to [8], in which in the step (C), a concentration of the dopant in the dopant-containing layer is controlled in the height direction of the three-dimensional structure.

[16] The method for manufacturing a semiconductor device according to [15], in which the concentration of the dopant in the dopant-containing layer is decreased along a direction from an upper region to a lower region of the three-dimensional structure.

[17] The method for manufacturing a semiconductor device according to [16], in which the dopant is one of element B and element P.

[18] The method for manufacturing a semiconductor device according to [8], in which the three-dimensional structure includes a trench, and an aspect ratio (height dimension/width dimension) of the trench is 10 to 100.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating a method for forming a barrier layer and a method for manufacturing a semiconductor device according to an embodiment of the present disclosure.

FIGS. 2A-D are schematic diagrams illustrating an example of steps (A) to (D) in FIG. 1 , respectively.

FIG. 3 is a time chart of the method for manufacturing a semiconductor device in FIG. 1 .

FIGS. 4A-C are electron microscope images showing barrier layers formed in an upper region, a central region, and a lower region of a base layer, respectively when an application time of radio frequency (RF) power is 1.0 sec.

FIGS. 5A-C are electron microscope images showing barrier layers formed in an upper region, a central region, and a lower region of a base layer, respectively when an application time of the RF power is 0.05 sec.

FIG. 6 is a graph showing a relationship between a film thickness of the barrier layer and a concentration of a dopant (P) in a dopant diffusion layer of the base layer.

FIGS. 7A-B are schematic diagrams illustrating a modified example of the steps illustrated in FIGS. 2B and 2C.

FIGS. 8A-D are schematic diagrams illustrating another example of the method for manufacturing the semiconductor device of FIG. 2 .

FIGS. 9A-B are schematic diagrams illustrating a modified example of the steps illustrated in FIGS. 8B and 8C.

FIG. 10 is a schematic diagram illustrating a conventional method for manufacturing a semiconductor device.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings used in the following descriptions, there are cases in which characteristic parts are shown enlarged to facilitate understanding for the sake of convenience, and the shapes, dimensional ratios, and the like of the components are not limited to those illustrated.

FIG. 1 is a flowchart illustrating a method for manufacturing a semiconductor device according to an embodiment of the present disclosure, and FIGS. 2A to 2D are schematic diagrams illustrating an example of steps (A) to (D) in FIG. 1 , respectively.

As illustrated in FIG. 1 , the method for manufacturing a semiconductor device according to an embodiment of the present disclosure includes a step (A) of forming a base layer having a three-dimensional structure, a step (B) of forming a barrier layer on the base layer, a step (C) of forming a dopant-containing layer on the barrier layer by using an atomic layer deposition (ALD) process, and a step (D) of performing a heat treatment. The manufacturing method for the present embodiment includes the steps (A) to (D), but is not limited to this, and may include other steps. Hereinafter, each of the steps (A) to (D) will be described.

<Step (A)>

First, etching, such as deep etching, is performed on a substrate, thereby forming a base layer 10 having a three-dimensional structure in which a dopant is to be diffused (see FIG. 2A). Although not particularly limited, the base layer 10 is, for example, a channel region formed between source-drain electrodes. The three-dimensional structure provided on the base layer 10 is formed by, for example, a convex pattern and a concave pattern.

The three-dimensional structure may include a trench 20 having facing side surfaces and a bottom surface as a concave pattern. When the three-dimensional structure includes a trench, an aspect ratio (height dimension/width dimension) of the trench is not particularly limited, and for example, preferably 10 to 100, more preferably 50 to 100, and still more preferably 70 to 100.

The base layer 10 is formed of, for example, silicon (Si), but not limited to this, and may be formed of a material containing Si as a main component. The material containing silicon as a main component means a material having a silicon content of more than 50% by mass.

<Step (B)>

Next, at least one of a film thickness, a film quality, and a film type of the barrier layer is controlled in a height direction (also referred to as a depth direction) of the three-dimensional structure by using an atomic layer deposition (ALD) process. The ALD process in the step (B) is preferably a plasma enhanced atomic layer deposition (PEALD) process (hereinafter, also referred to as a PEALD process). This can control a film density, a film stress, and the like, and simplify supply of gas serving as a reactive species, shorten a cycle time, and the like, as compared to a thermal ALD process.

A “layer” in the barrier layer refers to a structure having a film thickness formed on a surface of the base layer or a synonym of “film”. The same applies to a dopant-containing layer described later. Details of the barrier layer will be described later.

In the present embodiment, a film thickness of the barrier layer 11A can be controlled in the height direction of the three-dimensional structure by using the PEALD process (see FIG. 2B). For example, the film thickness of the barrier layer 11A formed on side surfaces of the three-dimensional structure can be controlled by adjusting an application time of RF power.

Further, the film thickness of the barrier layer 11A with respect to a width direction (lateral direction) of the three-dimensional structure may be controlled by using the PEALD process. For example, by adjusting RF power and the application time of the RF power, the film thickness of the barrier layer 11A formed in the lateral direction of the three-dimensional structure of the base layer 10, that is, formed on a top surface of the three-dimensional structure can be controlled. The barrier layer 11A formed on the top surface of the three-dimensional structure is saturated after a certain period of time, and even when RF power and the application time of the RF power increase in order to control a rate of film forming reaction, the film thickness does not further increase. Therefore, in an upper region 10 a of the three-dimensional structure, a difference in film thickness between the barrier layer 11A formed on the top surface of the three-dimensional structure and the barrier layer 11A formed on the side surfaces can be kept within a certain range.

As a specific example of the step (B), for example, as illustrated in FIG. 3 , a barrier layer precursor is formed on the top and side surfaces of the three-dimensional structure by supplying, by a pulse, a barrier layer forming gas and a reactant-containing gas for generating a reaction active species to a reaction space in which the base layer 10 is placed, purging or evacuating the barrier layer forming gas and the reactant-containing gas, and then applying RF power in a pulse to the reaction space in a predetermined time. During the above step, a reactant-containing gas can be constantly supplied to the reaction space. The step of supplying the barrier layer forming gas and the reactant-containing gas, the step of performing purging, and the step of applying RF power are set to one cycle, and the cycle is performed one or more times, thereby forming the barrier layer 11A on the top surface, the side surfaces, and the bottom surface of the three-dimensional structure of the base layer 10.

The barrier layer forming gas is a gas obtained by vaporizing a film-forming material, and is for example, a Si-containing gas, a Ti-containing gas, or a Ge-containing gas. The reactant-containing gas is a reactive gas for generating a reaction active species by applying RF power and generating an oxygen plasma in the reaction space, and contains, for example, one or more selected from O₂, N₂O, H₂O, and N₂. The barrier layer precursor is a monomolecular layer formed by a reaction between an adsorbed molecule chemically adsorbed on the surface of the three-dimensional structure and the reaction active species such as a radical, and is formed of, for example, silicon oxide (SiO), titanium oxide (TiO), germanium oxide (GeO), silicon nitride (SiN), or silicon oxide (SiON). The barrier layer 11A is a layer formed by depositing one or more barrier layer precursors, and is formed of, for example, SiO, TiO, or GeO, as with the barrier layer precursor.

In the step (B), by supplying, in a pulse, the barrier layer forming gas and the reactant-containing gas to the reaction space, both of these gases can be supplied to the reaction space in a predetermined time. A pulse when supplying the barrier layer forming gas and a pulse when supplying the reactant-containing gas may be the same or different. Thereafter, the purging or evacuating is performed in a predetermined time, such that a gas containing unreacted substances or a gas containing products is discharged outside the reaction space. The RF power and the application time of the RF power can be combined in various ways depending on specifications and the like. The RF power is in a range of, for example, 50 W to 800 W, and the application time of the RF power in one cycle is, for example, 0.1 sec to 2 sec.

When the barrier layer precursor is formed of SiO, examples of the film-forming material can include organoaminosilane containing one or more bis(diethylamino)silane (BDEAS), tetrakis(dimethylamino)silane (4DMAS), tris(dimethylamino)silane (3DMAS), bis(dimethylamino)silane (2DMAS), tetrakis(ethylmethylamino)silane (4EMAS), tris(ethylmethylamino)silane (3EMAS), bis(tert-butylamino)silane (BTBAS), and bis(ethylmethylamino)silane (BEMAS).

Although the film thickness of the barrier layer 11A formed in the step (B) is not particularly limited, for example, the film thickness of the barrier layer 11A formed on the top surface of the three-dimensional structure is 5 nm or less, and the film thickness of the barrier layer 11A formed on the side surfaces of the three-dimensional structure is 0.1 nm to 5 nm. FIGS. 4A to 4C are electron microscope images showing the barrier layers formed in the upper region, the central region, and the lower region of the base layer, respectively when the application time of the RF power in one cycle is 1.0 sec. In the three-dimensional structure of FIGS. 4A to 5C, an aspect ratio (height dimension/width dimension) of the trench is 40, the barrier layer is formed of SiO, and the applied RF power is 50 W. As illustrated in FIGS. 4A to 4C, when the application time of the RF power is 1.0 sec, it can be confirmed that the barrier layer is formed on the top surface, the side surfaces, and the bottom surface of the three-dimensional structure. Further, it can be confirmed that the barrier layer formed on the side surfaces of the three-dimensional structure becomes thinner along a direction from the top surface to the bottom surface of the three-dimensional structure.

Next, FIGS. 5A to 5C illustrate a case where the application time of the RF power in one cycle is 0.05 sec. In this case, it can be confirmed that the barrier layer is formed on the top and side surfaces of the three-dimensional structure (see FIGS. 5A to 5C), and the barrier layer is formed with uneven film thickness on the bottom surface of the three-dimensional structure, or the barrier layer is not partially formed (see FIG. 5C). Further, it can be confirmed that the barrier layer formed on the side surfaces of the three-dimensional structure becomes thinner along the direction from the top surface to the bottom surface of the three-dimensional structure, and the entire of the barrier layer formed on the side surfaces of the three-dimensional structure is formed thinner as compared to a case where the application time of the RF power is 0.05 sec.

From the above results, it can be seen that the film thickness of the barrier layer 11A formed on the side surfaces of the three-dimensional structure is controlled by shortening the application time of the RF power. Further, it can be seen that, by setting the application time of the RF power in an appropriate range, the film thickness of the barrier layer 11A formed on the side surfaces of the three-dimensional structure is gradually decreased along the direction from the top surface to the bottom surface of the three-dimensional structure.

<Step (C)>

Next, a dopant-containing layer 12A is formed on the barrier layer 11A by using the ALD process (see FIG. 2C). The ALD process in the step (C) is preferably the PEALD process as in the step (B).

For example, as illustrated in FIG. 3 , a dopant-containing layer precursor is formed on the top and side surfaces of the three-dimensional structure by supplying, in a pulse, a dopant-containing layer forming gas and a reactant for generating a reaction active species to the reaction space, purging or evacuating the dopant-containing layer forming gas and the reactant, and then applying RF power in a pulse to the reaction space in a predetermined time. During the above step, a reactant-containing gas can be constantly supplied to the reaction space. The step of supplying the dopant-containing layer forming gas and the reactant, the step of purging, and the step of applying RF power are set to one cycle, and the cycle is performed one or more times, such that the dopant-containing layer 12A is formed on the barrier layer 11A.

The dopant-containing layer forming gas is a gas obtained by vaporizing a film-forming material, and is, for example, a P-containing gas or a B-containing gas. As in the step (B), the reactant-containing gas is a reactive gas for generating a reaction active species by applying RF power and generating an oxygen plasma in the reaction space, and contains, for example, one or more selected from O₂, N₂O, and H₂O. The dopant-containing layer precursor is a monomolecular layer formed by a reaction between the adsorbed molecule chemically adsorbed on the surface of the three-dimensional structure and a reactive species such as a radical, and is formed of, for example, phosphosilicate glass or borosilicate glass. The dopant-containing layer 12A is a layer formed by depositing one or the plurality of dopant-containing layer precursors, and is formed of, for example, phosphosilicate glass or borosilicate glass as with the dopant-containing layer precursor.

When the barrier layer precursor is formed of phosphosilicate glass, an organophosphorus compound containing, for example, one or more P(OCH₃)₃ and PO(C₂H₅O)₃ can be used as a film-forming material. When the barrier layer precursor is formed of borosilicate glass, an organoboron compound containing, for example, one or more B(C₂H₅O)₃ and B(CH₃O)₃ can be used as a film-forming material.

The film thickness of the dopant-containing layer 12A formed in the step (C) is decreased along a direction from the upper region 10 a to the lower region 10 b of the three-dimensional structure. Although not limited to this, the film thickness of the dopant-containing layer 12A may be uniform along the direction from the upper region 10 a to the lower region 10 b of the three-dimensional structure. The film thickness of the dopant-containing layer 12A is not particularly limited, and for example, the film thickness of the dopant-containing layer 12A formed on the top surface of the three-dimensional structure is 1 nm to 10 nm, and the film thickness of the dopant-containing layer 12A formed on the side surfaces of the three-dimensional structure is 1 nm to 10 nm.

<Step (D)>

Thereafter, the heat treatment is performed to diffuse the dopant contained in the dopant-containing layer 12A into the base layer 10 through the barrier layer 11A (see FIG. 2D). In the present embodiment, the concentration of the dopant contained in the dopant-containing layer 12A is substantially uniform along the direction from the upper region 10 a to the lower region 10 b of the three-dimensional structure. At this time, the dopant in the dopant-containing layer 12A is diffused into the base layer 10 through the barrier layer 11A of which the film thickness is controlled in the height direction of the three-dimensional structure, and thus it is possible to make the distribution or concentration of the dopant in the dopant diffusion layer 30 uniform in the height direction of the three-dimensional structure of the base layer 10. Thus, a conformal dopant diffusion layer 30 is formed on an entire surface layer portion of the three-dimensional structure of the base layer 10.

The heat treatment in the step (D) is, for example, an annealing treatment, and conditions of the annealing treatment are, for example, a treatment temperature of 800° C. to 1200° C. and a treatment time of 0.5 sec to 5 sec. Thus, a diffusion rate of the dopant from the dopant-containing layer 12A to the base layer 10 can be sufficiently increased. The dopant is a substance obtained by solid-state diffusion (SSD) into the base layer 10, and may be one of, for example, element B and element P.

Thereafter, the dopant-containing layer 12A and the barrier layer 11A after the dopant is diffused are removed by etching such as wet etching, and the process is completed. From a viewpoint of a simplification of steps and the like, the etching may not be performed on the dopant-containing layer 12A and the barrier layer 11A.

FIG. 6 is a graph showing the relationship between the film thickness of the barrier layer and the dopant concentration in the dopant diffusion layer of the base layer. In FIG. 6 , element P is used as an example of the dopant. As can be clearly seen from the graph of FIG. 6 , there is a correlation between the film thickness of the barrier layer and the dopant concentration. When the film thickness of the barrier layer is increased, the dopant concentration is decreased. Accordingly, by forming the barrier layer so that the film thickness of the barrier layer becomes thinner along the direction from the upper region to the lower region of the three-dimensional structure and diffusing the dopant in the dopant diffusion layer into the base layer through the barrier layer, the distribution or concentration of the dopant in the dopant diffusion layer can be uniform in the height direction of the three-dimensional structure of the base layer 10.

In the above embodiment, the film thickness of the barrier layer 11A is controlled in the step (B), but the film quality of the barrier layer may be controlled instead of controlling the film thickness of the barrier layer 11A.

For example, as illustrated in FIG. 7A, it is possible to form a barrier layer 11B having a different film quality along the direction from the upper region 10 a to the lower region 10 b of the three-dimensional structure. Dots of the barrier layer 11B in FIG. 7A show that the film quality is uneven. Thereafter, as illustrated in FIG. 7B, the dopant-containing layer 12A can be formed on the barrier layer 11B in the same manner as in the step (C).

The film quality of the barrier layer 11B can be controlled by, for example, adjusting RF power and the application time of the RF power. Specifically, denseness of the barrier layer 11B can be changed by setting RF power and the application time of the RF power to a value in an appropriate range. As a result, the diffusion of the dopant can be controlled when the dopant in the dopant-containing layer 12A passes through the barrier layer 11B in the step (C). In particular, it is considered that by reducing the denseness of the barrier layer 11B formed on the side surfaces of the three-dimensional structure along the direction from the upper region 10 a to the lower region 10 b of the three-dimensional structure, it is possible to make the distribution of the dopant in the dopant diffusion layer 30 uniform in the height direction of the three-dimensional structure of the base layer 10.

In addition to controlling the film thickness of the barrier layer 11A, the film quality of the barrier layer 11A may be further controlled. Accordingly, the barrier layer 11A can be controlled with high precision, and it is possible to make the distribution of the dopant in the dopant diffusion layer 30 more uniform in the height direction of the three-dimensional structure of the base layer 10.

In the step (B) of the above embodiment, the film type of the barrier layer 11A may be controlled instead of controlling the film thickness of the barrier layer 11A. The film type of the barrier layer is controlled by, for example, (a) forming the barrier layer with SiN having area selectivity or (b) forming the barrier layer with SiON and adjusting a concentration of element N.

Specifically, when the barrier layer is formed of SiN, the barrier layer can be formed by using the ALD process, and preferably, the PEALD process, basically in the same manner as in the step (B). That is, a barrier layer precursor is formed on the top and side surfaces of the three-dimensional structure by supplying, in a pulse, a barrier layer forming gas and a reactant-containing gas for generating a reaction active species to a reaction space in which the base layer 10 is placed, purging or evacuating the barrier layer forming gas and the reactant-containing gas, and then applying RF power in a pulse to the reaction space in a predetermined time. During the above step, a reactant-containing gas can be constantly supplied to the reaction space. The step of supplying the barrier layer forming gas and the reactant, the step of performing purging, and the step of applying RF power are set to one cycle, and the cycle is performed one or more times, thereby forming the barrier layer 11A on the top and side surfaces of the three-dimensional structure of the base layer 10.

The PEALD process is preferably a high pressure PEALD process. When the base layer 10 is brought into contact with a nitrogen plasma in the reaction space in the high-pressure PEALD process, a pressure in the reaction space is, for example, 20 Torr or more. Further, a reaction temperature is, for example, 100° C. to 650° C. The RF power at the time of generating the nitrogen plasma is, for example, 500 W to 1000 W.

When the barrier layer precursor is formed of SiN, the barrier layer forming gas is, for example, a Si-containing gas. The reactant-containing gas is a reactive gas for generating a nitrogen plasma in the reaction space, and contains, for example, one or more selected from NH₃, N₂H₄, a N₂/H₂ mixture, and N₂. The barrier layer precursor is formed of SiN.

In this case, examples of the film-forming material can include silyl halide containing one or more selected from HSiI₃, H₂SiI₂, H₃SiI, H₂Si₂I₄, H₄Si₂I₂, and H₅Si₂I. Another specific example of the film-forming material can include a silicon precursor or a Si precursor described in Japanese Unexamined Patent Application Publication, First Publication No. 2017-79327, which is incorporated as if fully set forth herein.

Due to the formation of a SiN film by using the PEALD process, the SiN film can be selectively formed on the surface of the three-dimensional structure of the base layer 10 as a barrier layer. For example, a film forming portion and a non-film forming portion can be provided on the side surface of the three-dimensional structure by using a difference between a wet etching rate of the side surface and a wet etching rate of the top and bottom surfaces. When RF power is reduced, the etching rate of the side surface is increased, and the etching rate of the top and bottom surfaces is decreased. On the other hand, when RF power is increased, the etching rate of the side surface is decreased, and the etching rate of the top and bottom surfaces is increased. Therefore, it is possible to adjust the difference between the etching rate of the side surface and the etching rate of the top and bottom surfaces by controlling RF power. Further, element N in the SiN film prevents the dopant in the SiN film from being diffused. Therefore, it is considered that by selectively forming the barrier layer on the side surface of the three-dimensional structure along the direction from the upper region 10 a to the lower region 10 b of the three-dimensional structure, it is possible to make the distribution of the dopant in the dopant diffusion layer 30 uniform in the height direction of the three-dimensional structure of the base layer 10.

When the barrier layer is formed of SiON, the reactant-containing gas, that is, the nitrogen-containing gas is supplied in a smaller amount than an ordinary supply amount, and thus the barrier layer precursor can be formed of SiON in the above step when the barrier layer is formed of SiN. In this case, the barrier layer forming gas and the reactant-containing gas are supplied in the same amount as in a case where the barrier layer is formed of SiN.

A SiON film contains element O in a larger amount than element N. A content of element N in the SiON film is, for example, 3 atom % to 20 atom % from the viewpoint of preventing the diffusion of the dopant.

Due to the formation of the SiON film by using the PEALD process, the concentration of element N contained in the SiON film as the barrier layer can be changed in a direction along the surface of the three-dimensional structure of the base layer 10. For example, by controlling RF power and/or application time used in the nitrogen plasma, the content of element N can be changed along an in-plane direction of the SiON film. Further, element N in the SiON film prevents the dopant in the SiON film from being diffused as in the case of forming the SIN film. Therefore, it is considered that by decreasing the concentration of element N contained in the SiON film along the direction from the upper region 10 a to the lower region 10 b of the three-dimensional structure, it is possible to make the distribution of the dopant in the dopant diffusion layer 30 uniform in the height direction of the three-dimensional structure of the base layer 10.

In addition to controlling the film thickness of the barrier layer 11A, the film type of the barrier layer 11A may be further controlled. Further, the film thickness, the film quality, and the film type of the barrier layer 11A may be controlled. Therefore, the barrier layer 11A can be controlled with higher precision, and it is possible to make the distribution of the dopant in the dopant diffusion layer 30 more uniform in the height direction of the three-dimensional structure of the base layer 10.

FIGS. 8A to 8D are schematic diagrams illustrating another example of the method for manufacturing a semiconductor device of FIG. 2 . The manufacturing method shown in FIGS. 8A to 8D is basically the same as the manufacturing method shown in FIGS. 2A to 2D, and the same components are denoted by the same reference numerals and description thereof will be omitted.

As illustrated in FIG. 8B, in the step (B), the barrier layer 11A is formed on the side surfaces of the three-dimensional structure as in FIG. 2B so that the film thickness of the barrier layer 11A is decreased along the direction from the upper region 10 a to the lower region 10 b of the three-dimensional structure by using the ALD process.

Next, in the step (C), a dopant-containing layer 12B is formed on the barrier layer 11A by using the ALD process (see FIG. 8C). At this time, a concentration of the dopant in the dopant-containing layer 12B can be controlled in the height direction of the three-dimensional structure. Dots of the dopant-containing layer 12B in FIG. 8C show that the concentration of the dopant is uneven. Specifically, the concentration of the dopant contained in the dopant-containing layer 12B is decreased along the direction from the upper region 10 a to the lower region 10 b of the three-dimensional structure. When the concentration of the dopant contained in the dopant-containing layer 12B is controlled, the film thickness of the dopant-containing layer 12B is not particularly limited, and may increase along the direction from the upper region 10 a to the lower region 10 b of the three-dimensional structure, may be substantially constant, or may decrease along the direction.

The diffusion amount of the dopant in the base layer 10 can be controlled depending on the variation in the concentration of the dopant in the dopant-containing layer 12B. Therefore, by forming the barrier layer 11A so that the film thickness of the barrier layer 11A becomes thinner along the direction from the upper region 10 a to the lower region 10 b of the three-dimensional structure and decreasing the concentration of the dopant in the dopant-containing layer 12B along the direction from the upper region 10 a to the lower region 10 b of the three-dimensional structure, it is possible to make the distribution or concentration of the dopant in the dopant diffusion layer 30 (see FIG. 8D) uniform in the height direction of the three-dimensional structure of the base layer.

FIGS. 9A and 9B are schematic diagrams illustrating a modified example of the steps illustrated in FIGS. 8B and 8C. In FIG. 8B, the film thickness of the barrier layer 11A is controlled in the height direction of the three-dimensional structure, but not limited to this. As illustrated in FIG. 9A, the barrier layer 11A may be formed on the side surfaces of the three-dimensional structure so that the film thickness of the barrier layer 11B becomes substantially uniform along the direction from the upper region 10 a to the lower region 10 b of the three-dimensional structure. At this time, one or both of the film quality and the film type of the barrier layer 11B can be controlled as in FIG. 7A and the like.

In this case, in the step (C), the dopant-containing layer 12B can be formed as in FIG. 8C so that the concentration of the dopant contained in the dopant-containing layer is decreased along a direction from the upper region 10 a to the lower region 10 b of the three-dimensional structure (see FIG. 9B). As described above, the film thickness of the dopant-containing layer 12B may be substantially constant along the direction from the upper region 10 a to the lower region 10 b of the three-dimensional structure, or may increase or decrease along the direction. According to this modified example, it is possible to make the distribution or concentration of the dopant in the dopant diffusion layer 30 (see FIG. 8D) more uniform in the height direction of the three-dimensional structure of the base layer 10.

As described above, according to the present embodiment, since at least one of the film thickness, the film quality, and the film type of the barrier layer 11A (11B) is controlled in the height direction of the three-dimensional structure of the base layer 10 by using the ALD process, it is possible to make the distribution or concentration of the dopant in the dopant diffusion layer 30 uniform in the height direction of the three-dimensional structure of the base layer 10 by diffusing the dopant in the dopant-containing layer 12A (12B) into the base layer 10 through the barrier layer. Therefore, even when the base layer 10 has a three-dimensional structure with a high aspect ratio, the dopant can be uniformly distributed in the base layer.

Although the embodiment of the present disclosure have been described in detail with reference to the drawings, the specific configuration is not limited to the embodiments, and various modifications and substitutions may be made without departing from the gist of the present disclosure. The components described in the above embodiment may be combined.

For example, in the above embodiment, the barrier layer and the dopant-containing layer are formed by using the PEALD process (steps (B) and (C)), but not limited to this, and the barrier layer and the dopant-containing layer may be formed by using a thermal atomic layer deposition (ALD) process. In this case, for example, in the step (B), a barrier layer precursor can be formed on the top and side surfaces of the three-dimensional structure by supplying the barrier layer forming gas to the reaction space in which the base layer is placed, purging or evacuating the barrier layer forming gas, and then supplying the reactant-containing gas for generating the reaction active species, and performing thermal reaction in an oxygen atmosphere. Further, the barrier layer can be formed on the top and side surfaces of the three-dimensional structure of the base layer by performing the cycle one or more times.

As in the step (C), a dopant-containing layer precursor can be formed on the top and side surfaces of the three-dimensional structure by supplying a dopant-containing layer forming gas to the reaction space, purging or evacuating the dopant-containing layer forming gas, and then supplying the reactant-containing gas for generating the reaction active species, and performing thermal reaction in an oxygen atmosphere. Further, the dopant-containing layer can be formed on the barrier layer and the side surfaces of the three-dimensional structure of the base layer by performing the cycle one or more times.

The program for realizing the functions of a device (for example, an ALD device or a semiconductor manufacturing device) to which each manufacturing method according to the embodiment described above is applied may be recorded on a computer-readable recording medium (storage medium) so as to cause a computer system to read and execute the program recorded on this recording medium to thereby implement processing.

The “computer system” described here includes an operating system (OS) and hardware such as peripheral devices.

In addition, the “computer-readable recording medium” refers to a writable non-volatile memory such as a flexible disk, an optical magnetic disc, a read only memory (ROM), a flash memory, a transportable medium such as a digital versatile disk (DVD), and a storage device such as a hard disk incorporated in a computer system or the like. In addition, the recording medium may be, for example, a recording medium for temporarily recording data.

Furthermore, the “computer-readable recording medium” may maintain the program for a certain time, such as in an internal volatile memory (for example, dynamic random access memory (DRAM)) of the computer system as a server or a client when the program is transmitted via a communication line such as a telephone line or a network such as the Internet.

Further, the program may be transmitted from the computer system storing the program in the storage device to other computer systems through a transmission medium or by a transmission wave of the transmission medium. Here, the term “transmission medium” which transmits the program device a medium which is endowed with the function of transmitting information, such as a network (communication net) such as the internet or the like, or a communication line (communication channel) such as a telephone line or the like.

Further, the program may be a program for realizing a part of the functions described above. Further, the program may be a so called differential file (differential program) which is able to implement the above described function in combination with a program which is already recorded in the computer system.

In a computer, for example, a processor such as a central processing unit (CPU) reads and executes a program stored in a memory.

While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present disclosure. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims. 

What is claimed is:
 1. A method for manufacturing a semiconductor device, comprising: a step (A) of forming a base layer having a three-dimensional structure; a step (B) of forming a barrier layer on the base layer; a step (C) of forming a dopant-containing layer on the barrier layer by using an atomic layer deposition (ALD) process; and a step (D) of performing a heat treatment, wherein in the step (B), at least one of a film thickness, a film quality, and a film type of the barrier layer is controlled in a height direction of the three-dimensional structure by using the atomic layer deposition process, and in the step (D), a dopant contained in the dopant-containing layer is diffused into the base layer through the barrier layer, wherein in the step (C), a concentration of the dopant in the dopant-containing layer is decreased along a direction from an upper region to a lower region of the three-dimensional structure.
 2. The method for manufacturing a semiconductor device according to claim 1, wherein the step (B) is a plasma enhanced atomic layer deposition (PEALD) process.
 3. The method for manufacturing a semiconductor device according to claim 1, wherein in the step (B), the film thickness of the barrier layer formed on side surfaces of the three-dimensional structure is controlled by adjusting an application time of RF power.
 4. The method for manufacturing a semiconductor device according to claim 1, wherein in the step (B), the film thickness of the barrier layer formed on a top surface of the three-dimensional structure is controlled by adjusting RF power and an application time of the RF power.
 5. The method for manufacturing a semiconductor device according to claim 1, wherein in the step (B), the film quality of the barrier layer is controlled by adjusting RF power and an application time of the RF power.
 6. The method for manufacturing a semiconductor device according to claim 1, wherein in the step (B), the film type of the barrier layer is controlled by forming the barrier layer with SiN having area selectivity or forming the barrier layer with SiON and adjusting a concentration of element N.
 7. The method for manufacturing a semiconductor device according to claim 1, wherein in the step (C), the atomic layer deposition process is a plasma enhanced atomic layer deposition (PEALD) process.
 8. The method for manufacturing a semiconductor device according to claim 1, wherein the dopant is one of element B and element P.
 9. The method for manufacturing a semiconductor device according to claim 1, wherein the three-dimensional structure includes a trench, and an aspect ratio (height dimension/width dimension) of the trench is 10 to
 100. 10. The method for manufacturing a semiconductor device according to claim 1, wherein the step of forming the base layer comprises etching a substrate.
 11. The method for manufacturing a semiconductor device according to claim 1, wherein the base layer forms a channel region of the semiconductor device.
 12. The method for manufacturing a semiconductor device according to claim 1, wherein the three-dimensional structure includes a trench, and an aspect ratio (height dimension/width dimension) of the trench is 50 to
 100. 13. The method for manufacturing a semiconductor device according to claim 1, wherein the base layer comprises silicon.
 14. The method for manufacturing a semiconductor device according to claim 1, wherein the step (B) of forming the barrier comprises providing a Si-containing gas, a Ti-containing gas, or a Ge-containing gas.
 15. The method for manufacturing a semiconductor device according to claim 1, wherein the step (B) of forming the barrier comprises providing one or more reactants selected from O₂, N₂O, H₂O, and N₂.
 16. The method for manufacturing a semiconductor device according to claim 1, wherein the barrier layer comprises silicon oxide (SiO), titanium oxide (TiO), germanium oxide (GeO), silicon nitride (SiN), or silicon oxide (SiON).
 17. The method for manufacturing a semiconductor device according to claim 1, wherein the dopant-containing layer comprises phosphosilicate glass or borosilicate glass.
 18. The method for manufacturing a semiconductor device according to claim 1, wherein a temperature during the step (D) of performing a heat treatment is 800° C. to 1200° C.
 19. The method for manufacturing a semiconductor device according to claim 1, further comprising a step of removing the dopant-containing layer and the barrier layer. 